The overall goal of this Core is to enable diabetes-related research through the generation of unique, genetically-modified mutant mouse models. Our current organizational structure is composed of three distinct, but tightly interrelated Subcores: 1) the Molecular Subcore generates custom designed DNA and RNA constructs for genetic modification in mice and provides PCR genotyping as well as quantitation and localization of gene expression; 2) the Gene Targeting Subcore generates genetically modified mouse strains on a number of genetic backgrounds; and 3) the Diabetic Mouse Breeding Subcore maintains and interbreeds key strains of mutant (such as NOD) and/or genetically modified mice and distributes them to diabetes researchers within the DRC, including novel humanized models and genetically modified NOD strains generated by the Molecular and Gene Targeting Subcores. While the current structure of the Molecular Genetic Mouse Core remains ideally suited to the generation and characterization of animal models, our methodology has undergone a transformational shift in the last funding period with the development of CRISPR/Cas9 gene editing technology, which has, to a great extent, replaced our prior methods for generating animal models. The MGM Core has successfully generated a great many lines of genetically-modified mice related to diabetes studies, most recently using CRISPR-based technology, and its continuing focus on technological development will ensure that services to the diabetes community remain cutting-edge. In addition, a unique feature of this core is that the interests of the subcore directors have fueled a critical mass of resources for investigation of the rapidly developing research areas of the mechanistic relationships between gut microbiota, inflammasome biology and obesity, NAFLD, and type 1 and type 2 diabetes. The MGM Core has developed mouse models with altered innate immunity genes, including inflammasome-deficient NOD mice for the studies of type 1 diabetes, especially in association with the role of gut microbiota. Using these models, DRC investigators demonstrated the importance of commensal bacteria in type 1 diabetes development and implicated gut microbiota as an environmental modifier that influences diabetes onset. Also, mouse models of inflammasome-deficient B6 mice have been developed for studies of metabolic syndrome and type 2 diabetes. DRC investigators found that NLRP3 and NLRP6 inflammasomes negatively regulate NAFLD progression and obesity via modulation of the gut microbiota. To further enable such studies, the core has established gnotobiotic mouse strains in both B6 and NOD backgrounds, including some inflammasome-deficient strains. The gnotobiotic mouse is perhaps the ultimate tool for testing the effects of commensal bacteria on diabetes (type 1 and type 2) and metabolic syndrome development and intervention. Finally, the core has a continuing investment in extending and improving the development and application of technologies for humanization of the mouse genome for engraftment of CD34+ human HSC, and the reconstitution of a human hematopoietic and immune system. These ?humanized? mouse models will be invaluable tools for the dissection of the genetic components regulating the immunologic and metabolic responses in both type 1 and type 2 diabetes, especially with respect to human disease.